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Commit 54b7b868 authored by Angelo Ruocco's avatar Angelo Ruocco Committed by Jens Axboe
Browse files

cgroup: let a symlink too be created with a cftype file 



This commit enables a cftype to have a symlink (of any name) that
points to the file associated with the cftype.

Signed-off-by: default avatarAngelo Ruocco <angeloruocco90@gmail.com>
Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent c3e22192

include/linux/cgroup-defs.h

+3 −0
Original line number Diff line number Diff line
@@ -106,6 +106,8 @@ enum { 
	CFTYPE_WORLD_WRITABLE	= (1 << 4),	/* (DON'T USE FOR NEW FILES) S_IWUGO */

	CFTYPE_DEBUG		= (1 << 5),	/* create when cgroup_debug */



	CFTYPE_SYMLINKED	= (1 << 6),	/* pointed to by symlink too */



	/* internal flags, do not use outside cgroup core proper */

	__CFTYPE_ONLY_ON_DFL	= (1 << 16),	/* only on default hierarchy */

	__CFTYPE_NOT_ON_DFL	= (1 << 17),	/* not on default hierarchy */
@@ -543,6 +545,7 @@ struct cftype { 
	 * end of cftype array.

	 */

	char name[MAX_CFTYPE_NAME];

	char link_name[MAX_CFTYPE_NAME];

	unsigned long private;



	/*

kernel/cgroup/cgroup.c

+29 −4
Original line number Diff line number Diff line
@@ -1460,8 +1460,8 @@ struct cgroup *task_cgroup_from_root(struct task_struct *task, 


static struct kernfs_syscall_ops cgroup_kf_syscall_ops;



static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,

			      char *buf)

static char *cgroup_fill_name(struct cgroup *cgrp, const struct cftype *cft,

			      char *buf, bool write_link_name)

{

	struct cgroup_subsys *ss = cft->ss;
@@ -1471,13 +1471,26 @@ static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft, 


		snprintf(buf, CGROUP_FILE_NAME_MAX, "%s%s.%s",

			 dbg, cgroup_on_dfl(cgrp) ? ss->name : ss->legacy_name,

			 cft->name);

			 write_link_name ? cft->link_name : cft->name);

	} else {

		strscpy(buf, cft->name, CGROUP_FILE_NAME_MAX);

		strscpy(buf, write_link_name ? cft->link_name : cft->name,

			CGROUP_FILE_NAME_MAX);

	}

	return buf;

}



static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,

			      char *buf)

{

	return cgroup_fill_name(cgrp, cft, buf, false);

}



static char *cgroup_link_name(struct cgroup *cgrp, const struct cftype *cft,

			      char *buf)

{

	return cgroup_fill_name(cgrp, cft, buf, true);

}



/**

 * cgroup_file_mode - deduce file mode of a control file

 * @cft: the control file in question
@@ -1636,6 +1649,9 @@ static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft) 
	}



	kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));

	if (cft->flags & CFTYPE_SYMLINKED)

		kernfs_remove_by_name(cgrp->kn,

				      cgroup_link_name(cgrp, cft, name));

}



/**
@@ -3821,6 +3837,7 @@ static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp, 
{

	char name[CGROUP_FILE_NAME_MAX];

	struct kernfs_node *kn;

	struct kernfs_node *kn_link;

	struct lock_class_key *key = NULL;

	int ret;
@@ -3851,6 +3868,14 @@ static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp, 
		spin_unlock_irq(&cgroup_file_kn_lock);

	}



	if (cft->flags & CFTYPE_SYMLINKED) {

		kn_link = kernfs_create_link(cgrp->kn,

					     cgroup_link_name(cgrp, cft, name),

					     kn);

		if (IS_ERR(kn_link))

			return PTR_ERR(kn_link);

	}



	return 0;

}